Fluid-operated control device



June 13, 1961 u LANGHANS FLUID-OPERATED CONTROL DEVICE 2 Sheets-Sheet 1Filed Jan. 22, 1958 June 13, 1961 LANGHANS 2,988,099

FLUID-OPERATED CONTROL DEVICE Filed Jan. 22, 1958 2 Sheets-Sheet 2 Tlql-INVENTOR (/1. /?/C// 1 mv /M/vs United States Patent "'ce FLUID-OPERATEDCONTROL DEVICE Ulrich Langhans, Wansleben, Germany, assignor to VEBLeuna-Werke Walter Ulbricht, Merseburg, Germany Filed Jan. 22, 1958,Ser. No. 710,559 Claimsprioritnapplication Austria Aug. 8, 1957 4Claims. '(Cl. 13782) The invention relates to a fluid-operated controldevice and more specifically to a pressure-sensitive control deviceactuated by a fluid under pressure.

A wide variety of electrical sensing devices and relays are availablefor process control. Their installation, however, is sometimes costlywhere explosive or corrosiveatmospheres are encountered in the chemicalindustry so that the electrical devices need special enclosures.Electrical instruments under such conditions require special maintenanceand care, thus increasing the cost of operation. Pneumatic or hydrauliccontrols avoid many of these shortcomings.

It is the primary object of the invention to provide a control devicewhich releases sudden changes in fluid pressure in a container when thepressure in another container gradually reaches predetermined maximumand minimum values respectively.

It is further an object of the invention to provide a device adapted toactuate a mechanical element when the pressure in a container reaches apredetermined value.

It is another object of the invention to provide such a device whichwill act instantaneously when a predetermined pressure is attained.

Other features and advantages of the present invention will be apparentfrom the following detailed descrip' tion thereof when considered inconjunction with the attached drawing in which like reference numeralsin the several figures refer to the same or equivalent elements and inwhich FIG. 1 is a schematic vertical section of an embodiment of theinvention, and

FIGQZ is a schematic vertical section of the same embodiment as shown inFIG. 1, as applied to a different purpose.

Referring now to the drawings, FIG. 1 shows an embodiment of a device ofthe invention as applied to the control of the liquid level in a storagetank. A flexible airtight membrane 2 is rigidly mounted in a container 1which is thereby divided into two compartments. A baffie plate 3 isrigidly connected with membrane 2. A spring 23 theupper end of which isconnected to frame 20 and thelower part of which is adaptedto abutagainst baflie plate 3 protects membrane 2 against excessive deflectionby the upward movement of baffle plate 3. Pressure-sensitive resilientmetallic bellows 4are fastened at their lower end to the frame 20 of thedevice whereas the upper end forms a stem which is equipped with adischarge nozzle 5 and is slidably mounted in a transverse member 21 ofthe frame 20. Two adjustable stops 6 mounted on the upper stem ofbellows 4 and cooperating with transverse member 21 limit the axialupward and downward movements respectively of the bellows. Apressure-reducing device shown here as valve 8 supplies compressed airat constant pressure from a feed pipe 22 simultaneously to bellows 4 andto a pressure-actuated device, in this case to a pneumatically operatedvalve 7 biased by a spring towards the open position. A capil lary tube9 restricts the rate at which air may flow from pressure-reducing device8 to bellows 4. A tank 10 whose level is to be controlled by the deviceof the invention is equipped with a bubbling pipe 11 the outlet orificeof which is arranged below the minimum level to which the liquid in tank10 is permitted to drop. Bubbling Patented June 13, 1961 pipe-11 issupplied with compressed air from feed line 22 through reducing valve 8and through a capillary tube and needle valve 12, or communicates withthe upper airtight compartment of container 1.

In operation of the aforedescribed device, liquid is admit-ted in thedirection of the arrow through valve 7 into tank 10. As' the liquidlevel in the tank rises, the pressure increases in pipe 11 and thereforealso in the upper compartment of container -1. The membrane 2 yields andis displaced downward, thereby moving baflle plate 3 towards nozzle 5. AAt a predetermined hydrostatic pressure in tanicltl the gap betweenbaflie plate 3 and nozzle 5 becomes sufiiciently small to interfere withthe discharge of air from nozzle 5, the air pressure in bellows 4increases and causes axialexpansion of the bellows. A tight seal isformed between nozzle 5 and baffle plate 3 and the full pressure forwhich reducing valve 8 is set is almost instantaneously brought to bearon bellows 4 and also on pneumatic valve 7, thereby shutting off theflow of liquid to tank 10.

When the level of liquid in tank 10 drops, the pressure in pipe 11 andtherefore in the upper compartment of container 1 decreases. Themembrane 2; moves upward and takes baflie'plate. 3 along. However, thenozzle 5 is not at once released from plate 3 and pressure remains high.Only when the lower stop 6 abuts against transverse member 21, willpressure in bellows 4 decrease, since agap will be formed between nozzle5 and bafiie plate 3, which permits air to escape from bellows 4 leadingto a drop in pressure therein and to their elastic contraction. Thereturn spring in valve 7 then is able to open the valve against thesuddenly reduced pneumatic pressure and a new cycle is started.

It can readily be appreciated that the maximum and minimum liquid levelsin tank 10 can be set by suitably adjusting the two stops 6.

FIG. 2 illustrates on embodiment of the device of the invention as usedfor a pneumatic timing mechanism. A container 1 is divided by a flexiblemembrane 2 into two compartments. The upper compartment communicateswith an airtight storage vessel 13 and through a capillary tube orneedle valve 15 with a pneumatically operated pressure-release valve 16which is spring-biased towards the closed position. Membrane 2 carries abaflie plate 3 which cooperates with a nozzle 5 connected to bellows 4whose movements are limited by stops 6 abutting against transversemember 21 of frame 20. Membrane 2 is secured against excessive upwardpressure of bafiie plate 3 by spring 23, the upper end of which isconnected to frame 20 while the free lower end is adapted to abutagainstplate 3. Bellows 4 andpneumaticvalves 7 and 16 are all suppliedwith compressed air through a capillary tube 9 from a pressure reducingvalves connected to feed pipe 22. Storage vessel 13 is charged withcompressed air from the 'valve 8 through a capillary tube or needlevalve 14.

Vessel 13 is gradually charged with compressed air and the pressure fromabove on membrane 2 rises accordingly. When the pressure reaches apredetermined value, the membrane 2 pushes the bafiie plate 3 againstnozzle 5 so as to interfere with the discharge of air from bellows 4 inthe same manner as described in connection with the device of FIG. 1.The bellows expand suddenly and nozzle 5 is tightly sealed off. Theresulting pressure increase in the line supplying air to bellows 4causes valve 7 to close and valve 16 to open. Air then bleeds fromvessel 13 through valve 16 at a rate determined by needle valve 15 untilthe pressure in vessel 13 drops to a predetermined minimum value. Atthis time, the lower stop '6 will abut against transverse member 21 andcause a gap to be formed between nozzle 5 and baflie plate 3, whichpermits air to escape from bellows 4 leading to a drop in pressuretherein and to their elastic contraction. The pressure acting uponvalves 7 and 16 drops, thus permitting valve 7 to open and valve 16 toclose. A new cycle begins with the charging of vessel 13.

The time required for charging vessel 13 depends on the setting ofneedle valve 14. The time required for discharge of air from vessel 13is controlled by needle valve 15. It is furthermore possible to adjuststops 6 for the maximum and minimum pressures at which the device of theinvention will actuate valve 7. It is apparent that the timing cycle ofthe device can be varied readily with wide limits.

While the timing device of the invention is illustrated in FIG. 2 inconnection with the opening and closing of a pressure-operated valve 7,it will be obvious to those skilled in the art that otherpressure-sensitive devices of any kind may be actuated at predeterminedintervals by the device of the invention.

While air pressure was shown in the illustrative examples to act uponthe pressure-responsive membrane 2 and the pressure-responsive bellows 4of the embodiment of the invention, it is within the scope of theinvention to utilize the variations in pressure exerted by fluids of anykind to trigger the action of the control device. The pressure exertedby fluids other than air may be suddenly changed by the device of theinvention and such change may be utilized to actuate devices of any kindsuch as electrical pressure switches, hydraulic motors, or the like.

Because of its simplicity and ruggedness, the control device of theinvention permits maintenance-free operation over long periods of time.The moving parts do not require lubrication and are not impaired intheir function by unfavorable environmental conditions.

It should be understood, of course, that the foregoing disclosurerelates only to preferred embodiments of the invention and that it isintended to cover all changes and modifications of the examples of theinvention herein chosen for the purposes of the disclosure, which do notconstitute departures from the spirit and scope of the invention.

What is claimed is:

l. A pilot control device adapted to be connected by conduit means to asource of fluid operating pressure and to an apparatus similarlyconnected to said source, said pilot control device serving to controlthe pressure of said apparatus and comprising a housing, a flexibleairtight membrane dividing said housing, said housing having an inletopening at one side of said membrane, a baffie plate connected to saidmembrane on the side opposite from'said inlet opening and movable withsaid membrane in proportion to pressure in said inlet opening, adividing wall extending across said housing in the region of said baffleplate and having an opening therein, a pressure sensitive expansiblebellows on the side of said wall opposite said bafiie plate, saidbellows having an inlet formed in one end to direct actuating fluid intosaid bellows and including on the other end an elongated tubularportion, said tubular portion being slidable in said opening andterminating in a nozzle opening directed towards said bafile plate, saidactuating fluid being discharged through said nozzle opening againstsaid bafile plate, the movement of said baffle plate being directedtowards said nozzle opening upon an increase in pressure, therebythrottling the discharge through said nozzle opening to elfect expansionof said bellows, and stop members on said tubular portion located oneach side of said dividing wall and being of greater size than saidopening in said wall, whereby to control the amount of movement of saidbellows in directions towards and away from said baflle plate, theexpansion of said bellows causing said tubular portion to move in adirection towards said bafile plate and to completely seal otf saidnozzle opening.

2. A pilot control device according to claim 1 including means to biassaid baflie plate in a direction towards said nozzle opening.

3. A pilot control device according to claim 1 wherein said bellows ismade of a metallic material immediately expansible upon restriction offlow from said nozzle opening to elfect sudden movement of said tubularportion in the direction of said baffle plate.

4. A pilot control device adapted to control pressure from a source by apressure operated control means, the operation of an apparatus withinpredetermined pressure limits, said pilot control device comprising ahousing having a partition wall with an aperture therein, reciprocablebafile plate means exposed to fluid pressure and reciprocable inresponse thereto, a pressure sensitive expansible bellows including atubular portion at one end slidable in said aperture and'terminating inan opening directed toward said baflie plate means, means for directingactuating fluid into the opposite end of said bellows for dischargethrough said opening against said baflle plate means, said baflle platemeans being movable toward said opening to restrict flow of said fluidtherethrough upon increase in pressure, said bellows being thereuponexpansible due to said increase in pressure, causing said tubularportion to move against said baffle plate means and to close off saiddischarge, and stop means on said tubular portion adapted to contactsaid wall and to limit movement of said bellows.

References Cited in the file of this patent UNITED STATES PATENTS2,339,469 Emanuel Jan. 18, 1944 2,568,506 Mercer Sept. 18, 19512,695,030 Rice Nov. 23, 1954 2,760,511 Greeff Aug. 28, 1956 2,803,258Dyson Aug. 20, 1957 2,833,411 Bosman et al May 6, 1958 FOREIGN PATENTS888,226 France Dec. 7, 1943

